For several decades those skilled in the oil and gas well art have utilized techniques for predicting the characteristics of oil and gas bearing formations.
One such technique, generally known as formation testing, entails the insertion of a testing string or conduit into a well, which well intersects a formation to be tested.
The conduit string is sealed to the well wall by a selectively operable packer. This sealing places the interior of the conduit string in communication with the formation, with the formation and interior of the conduit string being isolated from a well annulus which is located above the packer and encircles the conduit string.
Conventionally, rotary or linear reciprocations of the conduit string, or combined manipulations of this nature, or the utilization of separate actuating tools, have been employed to effect a sequence of testing operations.
This sequence of testing operations often entails the opening and closing of a valve in the conduit string, during which time the pressure of formation fluid flowing through the conduit string is measured. When the interior of the conduit string is closed, pressure of fluid below the closed portion of the conduit string will be measured as "closed-in" pressure. When the conduit string is opened, pressure formation flowing through the conduit string will be measured as "flowing" pressure.
In conjunction with such pressure measurements, it has been conventional to entrap a sample of formation fluid flowing through the conduit string. After the sample chamber has been trapped, the trapped sample has been moved, with the conduit string, through the well to a work site where the sample was analyzed, or transported to an analysis station.
The sample entrapping operation, like the pressure measuring operation, usually has requred manipulations of the conduit string and/or the use of a separate actuating tool.
Even in connection with conventional "dry land" operations, the conduit string manipulations generally utilized in conducting pressure evaluations and sample entrapment have created substantial difficulties and uncertainties. Indeed, the history of the testing art is replete with attempts to provide more reliable testing tools, with manipulations being reduced to a minimum level.
As the petroleum industry moved offshore in recent years, the problems involved in formation testing have assumed even greater difficulty and uncertainty. In addition to the conventional problems associated with formation testing, offshore operations introduced additional complications, some attributable to wave action induced movement of floating drilling vessels, from which vessels testing operations are often conducted.
With particular reference to offshore testing operations, but with a perspective directed to overall testing operations of an offshore or dry land nature, it has been a basic goal of the industry to provide a formation testing technique where the problems of conduit string manipulations would be eliminated or minimized and optimum control and safety maintained during a testing operation.
It is with respect to this basic goal that this invention is concerned.